Process for the synthesis of 9,9-bis(hydroxymethyl)fluorene

ABSTRACT

The present invention relates to a novel process for the synthesis of 9,9-bis(hydroxymethyl)fluorene. The syntheses from fluorene to 9,9-bis(hydroxy-methyl)fluorene via a hydroxymethylation and further to 9,9-bis(methoxymethyl)-fluorene via a etherification are known. 9,9-bis(methoxymethyl)fluorene is a compound that is used as an electron donor for Ziegler-Natta catalysts. The present invention is related to an improvement in the synthesis of 9,9-bis(hydroxymethyl)fluorene leading to a decrease in the amount of solvent used and an easier work up while achieving high yield and purity.

The present invention relates to a novel process for the synthesis of 9,9-bis(hydroxymethyl)fluorene (hereafter also called “HM-FLU”). The synthesis from fluorene via HM-FLU to 9,9-bis(methoxymethyl)fluorene (hereafter also called “MM-FLU”) is known. 9,9-bis(methoxymethyl)fluorene is a compound that is for example used as an electron donor for Ziegler-Natta catalysts. The process for preparing this MM-FLU compound from fluorene typically comprises two separate steps, which are each discussed below.

Step 1 of the synthesis from fluorene to 9,9-bis(methoxymethyl)fluorene relates to the hydroxymethylation of fluorene to 9,9-bis(hydroxymethyl)fluorene. This hydroxymethylation is typically carried out using paraformaldehyde in dimethyl sulfoxide (DMSO) as a solvent. An alcoholic solution of sodium alkoxide, such as sodium methoxide in methanol or sodium ethoxide in ethanol is used as a base. Typically, first a solution or dispersion of paraformaldehyde, DMSO and sodium alkoxide is prepared. Then a solution or dispersion of fluorene is added to this mixture. The reaction is usually carried out at very low temperatures in an ice bath. The reaction is usually worked up by quenching with hydrochloric acid, addition of water and then one or more steps of extraction, distillation and/or recrystallization.

EP 0 728 770 discloses a method using a large volume of DMSO and a reaction temperature of 0° C. Chen et al. “synthesis of 9,9′-bis(methoxymethyl)fluorene”, Transactions of Tianjin University, 2003, volume 9, issue 3, pages 226-227 discloses that the reaction is carried out at a temperature of between 13 and 15° C. and requires a large volume of DMSO. CN1336359 discloses a phase transfer catalytic synthesis (3-phases) using formaldehyde in DMSO and sodium ethoxide; followed by complex purification including azeotropic distillation, extractant recovery, filtration, and recrystallization for an intermediate product. The methods according to the prior art require large volumes of DMSO during the synthesis of HM-FLU which is difficult to recover. The use of large volumes of DMSO also increases the overall costs as it requires a large volume of water and work up solvents, such as toluene and ethyl acetate for a two stage work up, which is undesirable from a cost as well as environmental view.

In the pending European patent application EP 15170076.2, filed Jun. 1, 2015, of the present inventor and in the name of the present applicant an improved method for preparing HM-FLU from fluorene is disclosed comprising providing a mixture of paraformaldehyde, dimethylsulfoxide and a sodium alkoxide (e.g. sodium methoxide in methanol or sodium ethoxide in ethanol) and adding fluorene in solid form to said mixture to obtain 9,9-bis(hydroxymethyl)fluorene. The advantages of adding fluorene as solid, e.g. powder, have been descripted in that patent application and are the following: a largely reduced amount of DMSO is needed, a largely reduced amount of water is need, much less work-up solvents, such as toluene and ethyl acetate are needed. This method leads to reduction in costs as well as improved environmental friendliness. The present method is a further improvement to the process disclosed in EP 15170076.2 in order to further simplify the procedure and reduce the amount of environmentally unfriendly solvents even further.

It is an aim of the present invention to overcome these drawbacks of the prior art and provide a more simplified synthesis of 9,9-bis(hydroxymethyl)fluorene and subsequent 9,9-bis(methoxymethyl)fluorene (see step 2 below).

Step 2 of the synthesis from fluorene to 9,9-bis(methoxymethyl)fluorene relates to the etherification of 9,9-bis(hydroxymethyl)fluorene (HM-FLU) to 9,9-bis(methoxy-methyl)-fluorene (MM-FLU). According to some prior art documents a combination of methyl iodide and sodium hydride is used, e.g. in EP 0 728 770. In Chen et al. a different process is disclosed using sodium hydroxide solution and dimethyl sulfate as the alkylating agent and a tetrabutylammonium bromide phase transfer agent. CN1336359 discloses methylating the intermediate product using DMS (dimethyl sulfate) with a complex work up including washing, azeotropic distillation, solvent recovery, filtration, recrystallization, and drying. JP0995460 discloses accelerating the reaction of an alcohol with a sulfuric ester by using a two-layer reaction of a non-aqueous solvent with an aqueous alkali solution; e.g. a diol of fluorene, is brought into contact with a sulfuric ester (e.g. DMS) and a phase-transfer catalyst (e.g. tetramethyl ammonium halide) in a two-layer (non-aqueous/alkali aqueous) liquid to form the desired compound.The methods according to the prior art however lead to the partial decomposition of DMS during the reaction which will reduces the strength of alkali solution. This will lead to a lower yield.

It is another aim of the present invention to provide a process for preparing 9,9-bis(hydroxymethyl)fluorene in a high yield with a simple process. In is another aim of the present invention to provide a process for preparing 9,9-bis(hydroxy-methyl)fluorene having a high purity with a simple process.

One or more of these aims are achieved by a process according to the present invention.

SUMMARY

The present invention is related in a first aspect to a process for the synthesis of 9,9-bis(hydroxymethyl)fluorene from fluorene comprising providing a mixture of paraformaldehyde, dimethylsulfoxide (DMSO), toluene and a sodium alkoxide and adding fluorene as a solid to said mixture to obtain 9,9-bis(hydroxymethyl)fluorene.

The addition of toluene during this reaction allows a further reduction in the amount of DMSO needed compared to EP 15170076.2 and in addition eliminates the need for purification by extraction and/or recrystallization. It is reaction and purification in one.

In an embodiment of said first aspect, fluorene is added in the form of a powder.

In an embodiment of said first aspect, toluene is present in an amount of at most 600 milliliters per mole of fluorene used, such as in an amount of at most 550 millimeters per mole of fluorene used. Toluene may also be present in an amount of at most 500 millimeters per mole of fluorene used. It may be present in an amount of at least 400 or even at least 450 milliliters per mole of fluorene used.

In an embodiment of said first aspect, dimethylsulfoxide (DMSO) is present in an amount of at most 600 milliliters per mole of fluorene used. In an embodiment of said first aspect, dimethylsulfoxide (DMSO) is present in an amount of at most 550 milliliters per mole of fluorene used. In an embodiment of said first aspect, dimethylsulfoxide (DMSO) is present in an amount of at most 500 milliliters per mole of fluorene used. In an embodiment, the amount of dimethylsulfoxide (DMSO) is present in an amount of at least 400, such as at least 450 milliliters per mole of fluorene used.

In an embodiment of said first aspect, paraformaldehyde is used in an amount of between 1.8 and 2.6 mole per mole of fluorene used.

In an embodiment of said first aspect, the sodium alkoxide is selected from sodium methoxide and sodium ethoxide. In an embodiment of said first aspect, the sodium alkoxide is sodium methoxide. In an embodiment of said first aspect, the sodium alkoxide is used as a sodium alkoxide solution in an alcoholic solution. In an embodiment of said first aspect, the sodium alkoxide is used as a sodium alkoxide solution in an alcoholic solution selected from sodium methoxide in methanol or sodium ethoxide in ethanol. In an embodiment of said first aspect, sodium alkoxide is used as a sodium alkoxide solution in an alcoholic solution, being sodium methoxide in methanol.

In an embodiment of said first aspect, said process comprises the following steps:

-   -   a) providing a mixture of paraformaldehyde, dimethylsulfoxide         and toluene;     -   b) adding a sodium alkoxide solution in an alcoholic solvent to         the mixture of step a);     -   c) adding fluorene as a solid to the mixture obtained in step         b);     -   d) allowing the mixture obtained in step c) to react;     -   e) quenching the mixture obtained in step d) by adding an acid;     -   f) mixing the mixture obtained in step e) with water to obtain a         suspension of 9,9-bis(hydroxymethyl)fluorene;     -   g) filtering said mixture of step f) to obtain         9,9-bis(hydroxy-methyl)fluorene.

In an embodiment of said first aspect, the acid used to quench the mixture in step e) is an inorganic acid. In an embodiment of said first aspect, the acid used to quench the mixture in step e) is hydrochloric acid. In an embodiment of said first aspect, the acid used to quench the mixture in step e) is concentrated hydrochloric acid. In an embodiment of said first aspect, water is added during step f) in an amount of between 1250 and 5000 milliliters water per mole of fluorene used.

In an embodiment of said first aspect, the process is carried out at a temperature between 10 and 20° C.

In an embodiment of said first aspect, the process comprises the following steps:

-   -   1) providing a mixture of between 1.8 and 2.6 mole of         paraformaldehyde per mole of fluorene used and at most 500         milliliters of dimethylsulfoxide per mole of fluorene used and         at most 500 milliliters of toluene per mole of fluorene used;     -   2) adding a sodium alkoxide solution in an alcoholic solvent to         the mixture of step 1) so that the amount of sodium alkoxide is         between 0.2 and 0.3 mole per mole of fluorene used;     -   3) over a period of between 5 and 30 minutes adding fluorene in         the form of a powder to the mixture obtained in step 2) at a         temperature between 10 and 20° C.;     -   4) allowing the mixture obtained in step 3) to react for a         period of between 10 and 50 minutes at a temperature of between         10 and 20° C.;     -   5) quenching the mixture obtained in step 4) by adding an acid         in an amount of between 10 and 20 milliliters per mole of         fluorene used;     -   6) mixing the mixture obtained in step 5) with water in an         amount of between 1250 and 5000 milliliters water per mole of         fluorene used for a period of between 10 and 50 minutes to         obtain a suspension of 9,9-bis(hydroxymethyl)fluorene;     -   7) filtering said mixture of step 6) to obtain         9,9-bis(hydroxy-methyl)fluorene.

The present invention is related in a second aspect to a process for the synthesis of 9,9-bis(methoxymethyl)fluorene from fluorene, comprising the steps of:

-   -   I) providing a mixture of paraformaldehyde, dimethylsulfoxide,         toluene and a sodium alkoxide and adding solid fluorene to said         mixture to obtain 9,9-bis(hydroxymethyl)fluorene,     -   II) providing an alkali metal hydroxide solution, mixing said         solution with tetra-alkylammonium halide,         9,9-bis(hydroxymethyl)fluorene obtained in step I) and a solvent         and adding dimethyl sulfate to obtain         9,9-bis(methoxymethyl)fluorene wherein dimethyl sulfate is added         in at least three portions wherein the reaction mixture is         stirred for a period of at least 60 minutes before the following         portion is added.

In an embodiment of said second aspect, as the alkali metal hydroxide, sodium hydroxide is used. In an embodiment of said second aspect, as the alkali metal hydroxide, sodium hydroxide is used as a 40 to 50 wt. % solution in water.

In an embodiment of said second aspect, the halide in the tetra-alkylammonium halide is selected from the group consisting of chloride, bromide, fluoride, iodide and is preferably bromide. The bromide is preferred because it is widely available. In an embodiment of said second aspect, the alkyl groups in the tetra-alkylammonium halide are each independently selected from the group of C1-C12 alkyl, preferably C2-C8 alkyl, more preferably C3-C5 alkyl, such as n-propyl, isopropyl, n-butyl, iso-butyl, tert-butyl, n-pentyl, sec-pentyl, tert-pentyl, 3-pentyl, isopentyl, neopentyl, most preferably an n-alkyl, such as n-butyl. Preferably, all the alkyl groups are the same. In an embodiment of said second aspect, as the tetra-alkylammonium halide tetra-n-butylammonium bromide is used.

In an embodiment of said second aspect, dimethyl sulfate is added in at least four portions. In an embodiment of said second aspect, dimethyl sulfate is added in at least five portions. In an embodiment of said second aspect, dimethyl sulfate is added in a total amount of between 2 and 6 moles per mole of 9,9-bis(hydroxymethyl)fluorene used.

In an embodiment of said second aspect, as the solvent toluene is used.

In an embodiment of said second aspect, said process comprises the steps of

-   -   a) providing a mixture of paraformaldehyde, dimethylsulfoxide         and toluene;     -   b) adding a sodium alkoxide solution in an alcoholic solvent to         the mixture of step a);     -   c) adding fluorene as a solid to the mixture obtained in step         b);     -   d) allowing the mixture obtained in step c) to react;     -   e) quenching the mixture obtained in step d) by adding an acid;     -   f) mixing the mixture obtained in step e) with water to obtain a         suspension of 9,9-bis(hydroxymethyl)fluorene;     -   g) filtering said mixture of step f) to obtain         9,9-bis(hydroxymethyl)fluorene;     -   h) providing a solution of sodium hydroxide in water;     -   i) adding to the solution of step h)         9,9-bis(hydroxymethyl)fluorene obtained in step g),         tetra-alkylammonium halide and a solvent;     -   j) stirring the mixture obtained in step i);     -   k) adding dimethyl sulfate in at least three portions, wherein         the resulting reaction mixture obtained is stirred for a certain         period of time before the following portion is added;     -   l) continue stirring the reaction mixture obtained in k);     -   m) adding water to the mixture obtained in step I) and stirring;     -   n) separate the mixture obtained in step m) in an organic layer         and a water layer, obtain the organic layer and wash the organic         layer with water;     -   o) separate the mixture obtained in step ni) in an organic layer         and a water layer, obtain the organic layer and remove the         solvent to obtain crude 9,9-bis(methoxymethyl)fluorene.

In an embodiment of said second aspect, the crude 9,9-bis(methoxymethyl)fluorene obtained in step vii) is recrystallized to obtain 9,9-bis(methoxymethyl)fluorene.

In an embodiment of said second aspect, in step k) each portion of dimethyl sulfate is added over a period of between 15 and 60 minutes. In an embodiment of said second aspect, in step k) between the addition of each portion the reaction mixture is stirred for a period of between 60 and 120 minutes.

In an embodiment of said second aspect, step I) is carried out for a period of between 16 and 30 hours. In an embodiment of said second aspect, step k) and/or step I) are carried out at a temperature of between 15 and 35° C.

In an embodiment of said second aspect, said process comprises the steps of

-   -   1) providing a mixture of between 1.8 and 2.6 mole of         paraformaldehyde per mole of fluorene used and at most 500         milliliters of dimethylsulfoxide per mole of fluorene used and         at most 500 milliliters of toluene per mole of fluorene used;     -   2) adding a sodium alkoxide solution in an alcoholic solvent to         the mixture of step 1) so that the amount of sodium alkoxide is         between 0.2 and 0.3 mole per mole of fluorene used;     -   3) over a period of between 5 and 30 minutes adding fluorene in         the form of a powder to the mixture obtained in step 2) at a         temperature between 10 and 20° C.;     -   4) allowing the mixture obtained in step 3) to react for a         period of between 10 and 50 minutes at a temperature of between         10 and 20° C.;     -   5) quenching the mixture obtained in step 4) by adding an acid         in an amount of between 10 and 20 milliliters per mole of         fluorene used;     -   6) mixing the mixture obtained in step 5) with water in an         amount of between 1250 and 5000 milliliters water per mole of         fluorene used for a period of between 10 and 50 minutes to         obtain a suspension of 9,9-bis(hydroxymethyl)fluorene;     -   7) filtering said suspension of step 6) to obtain         9,9-bis(hydroxy-methyl)fluorene;     -   8) providing a solution of between 40 and 50 wt. % of sodium         hydroxide in water so that between 2.5 and 7.5 mole of sodium         hydroxide is present per mole of         9,9-bis(hydroxymethyl)fluorene—obtained in step 7) used;     -   9) adding to the solution in step 8) the following:         9,9-bis(hydroxy-methyl)fluorene obtained in step 7),         tetra-n-butylammonium bromide in an amount of 0.005 and 0.025         mole per mole of 9,9-bis(hydroxymethyl)fluorene used and toluene         in an amount of between 800 and 1500 milliliter per mole of         9,9-bis(hydroxy-methyl)fluorene used;     -   10) stirring the mixture obtained in step 9) for a period of         between 1 and 5 hours at a temperature between 15 and 30° C.;     -   11) adding dimethyl sulfate in a total amount of between 2 and 6         moles per mole of 9,9-bis(hydroxymethyl)fluorene in between 3 to         6 portions, wherein each portion is added over a period of         between 15 and 60 minutes and wherein the resulting reaction         mixture is stirred for a period of between 60 and 120 minutes         before the following portion is added and wherein the addition         is carried out at a temperature between 15 and 35° C.;     -   12) continue stirring the reaction mixture obtained in 11) for a         period of between 16 and 30 hours at a temperature between 15         and 35° C.;     -   13) adding water to the mixture obtained in step 12) in an         amount of between 400 and 750 milliliter per mole of         9,9-bis(hydroxymethyl)fluorene used and stirring for a period of         time between 5 and 25 minutes at a temperature between 15 and         35° C.;     -   14) separate the mixture obtained in step 13) in an organic         layer and a water layer, obtain the organic layer and wash the         organic layer with between 100 and 500 milliliter water per mole         of 9,9-bis(hydroxymethyl)fluorene used;     -   15) separate the mixture obtained in step 14) in an organic         layer and a water layer, obtain the organic layer and remove the         solvent by distillation to obtain crude         9,9-bis(methoxymethyl)fluorene;     -   16) optionally recrystallize the crude         9,9-bis(methoxymethyl)fluorene from between 300 and 600         milliliter methanol per mole of 9,9-bis(hydroxy-methyl)fluorene         used and dry under vacuum to obtain         9,9-bis(methoxymethyl)fluorene.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is related to a novel method of preparing 9,9-bis(hydroxymethyl)fluorene, an intermediate in the preparation of 9,9-bis(methoxymethyl)fluorene, without the need of separate purification steps.

The drawing below shows schematically the two steps from fluorene to 9,9-bis(methoxymethyl)fluorene.

Step 1: Preparation of 9,9-bis(hydroxymethyl)fluorene

The present inventors have observed that by the addition of toluene during the first reaction step, the total amount of solvent needed during the synthesis and during the work-up can be decreased dramatically while obtaining the desired 9,9-bis(hydroxymethyl)fluorene in high yield and high purity. The work up procedure is simplified by this inventive method since no purification steps are required. The reaction mixture after quenching and suspension may be filtered to obtain the product directly, without any further extraction and/or recrystallization. This 9,9-bis(hydroxymethyl)fluorene can be used further in the synthesis of 9,9-bis(methoxymethyl)fluorene that can be used for example as an electron donor in Ziegler-Natta catalytic systems.

The key feature of the first aspect of the present invention is the use of toluene as a solvent during the first step in the process, in preparing HM-FLU. In an embodiment of said first aspect, fluorene is added in the form of a powder. “Powder” as used in the present invention means: a solid substance composed of a large number of fine particles that may flow freely. It is in crystalline form. With fine particles is meant particles passing through a 50-100 mesh (viz. sieve of about 300 to about 150 micrometer). In other words, the particles have a diameter of between about 150 and about 300 micrometer, preferably at least 70%, more preferably 80%, more preferably 90%, even more preferably 95% of the particles have a diameter that lies in the range of between about 150 and about 300 micrometer. The use of fluorene in powder form has proven to be very effective and ensures a good reaction rate and homogeneity. A high yield is obtained.

It is also possible that fluorene is added in the form of a granulate or flakes. “granulate” as used in the present invention means: a solid substance composed of a large number of large particles that may flow freely. It is in crystalline form. With large particles is meant particles having a diameter of between about 300 micrometer and about 4.0 millimeter, preferably at least 70%, more preferably 80%, more preferably 90%, even more preferably 95% of the particles have a diameter that lies in the range of between about 300 micrometer and about 4.0 millimeter.

In an embodiment, in step 1 DMSO is present in an amount of at most 7.5, preferably at most 6, more preferably at most 4 milliliter per gram of fluorene, at least 3 milliliter per gram of fluorene.

The present inventors have observed that when fluorene is added as a solid and when toluene is added as a solvent a good yield may be obtained and a high purity product without the need, while ensuring less environmental and health issues by the reduced volume of DMSO.

In an embodiment of said first aspect, the molar ratio between fluorene and paraformaldehyde is between 1 to 1 and 1 to 3, preferably between 1 to 1.8 and 1 to 2.6. In an embodiment of said first aspect, paraformaldehyde is used in an amount of between 1.8 and 2.6 mole per mole of fluorene used. Most preferably, between 2.2 to 2.4 mole of paraformaldehyde per mole of fluorene is used, such as 2.3 mole. The present inventors have observed that such an amount leads to a good yield of the product and a low amount of side products.

In an embodiment of said first aspect, the sodium alkoxide is selected from sodium methoxide and sodium ethoxide, preferably sodium methoxide. In an embodiment of said first aspect, the sodium alkoxide is used as a sodium alkoxide solution in an alcoholic solution, preferably selected from sodium methoxide in methanol or sodium ethoxide in ethanol, more preferably sodium methoxide in methanol.

In an embodiment, the molar ratio between fluorene and sodium alkoxide is between 1 to 0.1 and 1 to 0.5, preferably between 1 to 0.2 and 1 to 0.3. The advantage thereof is that high yields are obtained and the formation of side product, such as the dimer product 9,9′-methylenedifluorene is reduced significantly.

In an embodiment, the sodium alkoxide is present in the form of a solution in an alcohol, preferably in an amount of between 10 to 50 wt. %, preferably between 20 and 40 wt. %, between 25 and 35 wt. %, wherein the percentage is a weight percentage based on the total weight of the solution. For example a solution in methanol of sodium methoxide, more preferably as a 25 to 35 wt. % solution in methanol. The sodium alkoxide solution is either prepared freshly or commercially obtained. When the concentration of the solution is lower, a lower yield will be obtained.

In embodiments of said first aspect, said process comprises the steps a) to g) or 1) to 7) as discussed above. The present inventors have observed that this specific sequence of process steps provides good results.

In an embodiment of said first aspect, the acid used to quench the mixture in step e) is an inorganic acid, preferably hydrochloric acid, more preferably concentrated hydrochloric acid. However, a acidic solution of 10-20% may also be used.

In an embodiment of said first aspect, water is added during step f) in an amount of between 1250 and 5000 milliliters water per mole of fluorene used.

In an embodiment of said first aspect, the process is carried out at a temperature between 10 and 20° C. The advantage thereof is that the reaction rate is optimal and also that the production of the dimer side product, viz. 9,9′-methylenedifluorene is significantly reduced.

In an embodiment of said first aspect, fluorene is added over a period of between 5 and 30 minutes, preferably between 10 and 20 minutes, more preferably between 13 and 17 minutes.

In an embodiment of said first aspect, the reaction time after addition of fluorene is between 10 and 50 minutes, more preferably between 20 and 40 minutes, even more preferably between 25 and 35 minutes.

In an embodiment of said first aspect, the mixture of paraformaldehyde, dimethylsulfoxide, toluene and a sodium alkoxide is kept at a temperature between 10 and 20° C., preferably between 12 and 17° C. during the addition of fluorene.

In an embodiment of said first aspect, the mixture of paraformaldehyde, dimethylsulfoxide, toluene, sodium alkoxide and fluorene is kept at a temperature between 10 and 20° C., preferably between 12 and 17° C. during the reaction after completion of the addition of fluorene.

In an embodiment of said first aspect, the reaction is quenched to obtain a quenched reaction mixture by adding an acid, preferably hydrochloric acid, more preferably concentrated hydrochloric acid. Preferably, acid is used in an amount of between 0.05 to 0.15 milliliters per gram of fluorene used. In an embodiment, acid is used in an amount of between 10 and 20 milliliters per mole of fluorene used.

In an embodiment of said first aspect, the quenched reaction mixture is worked up by adding water of by adding the quenched reaction mixture to water in order to obtain a suspension of reaction product in water; preferably water is used in an amount of at least 5, preferably at least 10, preferably at most 20, preferably at most 15, more preferably at most 12 milliliters per gram of fluorene used.

In an embodiment of said first aspect, the suspension of reaction product is stirred between 10 and 50 minutes, more preferably between 20 and 40 minutes, even more preferably between 25 and 35 minutes. In an embodiment of said first aspect, a reaction product is obtained after filtration of said suspension of reaction product.

Step 2: Preparation of 9,9-bis(methoxymethyl)fluorene

The present invention is related in a second aspect to a novel method of preparing 9,9-bis(methoxymethyl)fluorene. The method according to the prior art add the total volume of dimethyl sulfate, either at once or drop wise, during one single period of time. The present inventors have observed that it is advantageous to add the total amount of dimethyl sulfate is at least three discrete portions wherein there is a reaction or wait time, preferably of at least 60 minutes, in between the addition of each portion. The reason for this is if it is added in one lot dimethyl sulfate partly will decompose and also reduce strength of alkali not allowing further reaction happening. The present inventor have inventively found out that if DMS is added too slow or drop wise it will hydrolyze and required more, which is undesirable. The present invention solves this problem by adding it in lots or portions. In an embodiment DMS is first diluted with a solvent, such as toluene, prior to being added to the reaction mixture.

The two aspects of the present invention may be combined by first preparing 9,9-bis(hydroxymethyl)fluorene prepared according to the process in the first aspect of the present invention and subsequently preparing 9,9-bis(hydroxymethyl)fluorene.

In an embodiment of said second aspect, as the alkali metal hydroxide sodium hydroxide is used, preferably as a 40 to 50 wt. % solution in water. The advantage thereof is that the reaction rate is higher when the concentration of the hydroxide solution is in this range. In the concentration decreases, the reaction rate also decreases. In an embodiment of said second aspect, as the tetra-alkylammonium halide tetra-n-butylammonium bromide is used. This compound provides a good effect and is readily available commercially. In an embodiment of said second aspect, dimethyl sulfate is added in at least four portions, such as in at least five portions. The advantage thereof is that the decomposition of DMS is further reduced.

In an embodiment of said second aspect, dimethyl sulfate is added in a total amount of between 2 and 6 moles per mole of 9,9-bis(hydroxymethyl)fluorene used. The advantage thereof is that on the one hand a good yield and purity is obtained and on the other hand the amount is limited so as to decrease the costs. In an embodiment of said second aspect, as the solvent toluene is used. The advantage thereof is that the product is very soluble in toluene. Another solvent may be used and selected by a person skilled in the art, based on the solubility of the product.

In an embodiment of said second aspect, a solution of between 40 and 60 wt. %, preferably between 45 and 55 wt. % of alkali metal (preferably sodium) hydroxide in water is used. In an embodiment of said second aspect, the molar ratio between alkali metal (preferably sodium) hydroxide and HM-FLU is between 2.5 to 1 and 7.5 to 1, preferably between 4 to 1 and 6 to 1. In an embodiment of said second aspect, tetra-n-butylammonium bromide is used in an amount of between 0.005 and 0.025 mole per mole of HM-FLU used. In an embodiment of said second aspect, toluene is used in an amount of between 800 and 1500 milliliter per mole HM-FLU used.

In an embodiment of said second aspect, the mixture of step 9) is stirred in step 10) for a period of between 1 and 5 hours, preferably between 2 and 4 hours. In an embodiment of said second aspect, the mixture of step 9) is stirred in step 10) at a temperature between 15 and 30° C., preferably between 20 and 25° C. In an embodiment of said second aspect, the dimethyl sulfate is added in a total amount of between 2 and 6 moles, preferably between 3 and 5, more preferably between 3.5 and 4.5 mole, per mole of 9,9-bis(hydroxymethyl)fluorene used. In an embodiment of said second aspect, the dimethyl sulfate is added in several portions, preferably substantially equal portions (viz. portions that have weights that are within +/−10% of each other). Preferably, between 3 to 6 portions, more preferably between 4 to 5 portions are used. The present inventor has found out that when using two portions, the reaction does not go to completion and more DMS is required which is undesirable. In an embodiment of said second aspect, each portion of dimethyl sulfate is added over a period of between 15 and 60 minutes, preferably 30 and 45 minutes.

In an embodiment of said second aspect, the reaction mixture after a portion of dimethyl sulfate is added is stirred for a period of between 60 and 120 minutes, preferably between 80 and 100 minutes, before the following portion of dimethyl sulfate is added. The conversion is checked by means of TLC (EtAc+Heptane-20+80). If the reaction is not complete it may be stirred for another few hours at room temperature. In an embodiment of said second aspect, the addition of the portions of dimethyl sulfate is carried out at a temperature between 15 and 35° C., preferably between 20 and 25° C. In an embodiment of said second aspect, after the addition of the final portion of dimethyl sulfate, the mixture is stirred for a period of between 16 and 30 hours, preferably between 20 and 25 hours, preferably at a temperature between 15 and 35° C., more preferably between 20 and 25° C.

In an embodiment of said second aspect, water is added for work up of the reaction mixture in an amount of between 400 and 700 milliliter water, preferably between 500 and 600 milliliter per mole of 9,9-bis(hydroxymethyl)fluorene used. In an embodiment of said second aspect, the worked up reaction mixture comprising water is stirred for a period of time between 5 and 25 minutes, preferably between 10 and 15 minutes. In an embodiment of said second aspect, the worked up reaction mixture comprising water is stirred at a temperature between 15 and 35° C., preferably between 20 and 25° C.

In an embodiment of said second aspect, the organic layer is removed from the water layer and washed with between 300 and 600 milliliter water, preferably between 400 and 500 milliliters water per mole of 9,9-bis(hydroxymethyl)fluorene used. In an embodiment of said second aspect, the organic layer is removed from the water layer and the solvent is removed by distillation to obtain crude 9,9-bis(methoxy-methyl)fluorene. In an embodiment of said second aspect, the crude 9,9-bis(methoxymethyl)fluorene is optionally recrystallized from between 400 and 700 milliliter methanol, preferably between 500 and 600 milliliter per mole of 9,9-bis(hydroxymethyl)fluorene used and dried under vacuum to obtain 9,9-bis(methoxymethyl)fluorene.

The present invention is further elucidated by means of the following non-limiting examples.

EXAMPLES Materials and Methods

All materials mentioned are obtained by commercial supplier and are readily available.

HPLC was measured using as mobile Phase-A 0.02% orthophosphoric acid and using as mobile Phase-B Acetonitrile. The HPLC Column used was a Hypersil BDS, C18, (250×4.6)mm, 5p. The measurement is done at a wavelength of 223 nm; a column oven temperature of 400° C.; an injection volume of 10 μl; a flow rate of 1.0 mL/min. As a diluent acetonitrile is used.

Example 1 Preparation of 9,9-bis(hydroxymethyl)fluorene

Dimethylsulfoxide (DMSO) (300 ml), toluene (300 ml) and paraformaldehyde (PF) (40 gram) were charged into a round bottom flask, mixed and cooled to a temperature of 13-15° C. Subsequently, sodium methoxide 30% solution (26 gram) was added to this mixture.

Gradually fluorene in powder form (100 gram, 0.6 mole) was added to above reaction mixture over a period of 15 minutes, while the temperature was maintained at 14-16° C. It was observed that most of the paraformaldehyde dissolves instantly upon addition of the fluorene. The resulting mixture was stirred for 30 minutes while the temperature was maintained at 14-16° C. The resulting mixture was a clear pale yellow solution.

Subsequently, concentrated HCl (8-10 ml) was added to the obtained solution until al neutral pH (pH 6-7) was reached in order to stop the reaction. To the reaction mass gradually water (1000 ml) is added and reaction mass is cooled to 10° C. for 3 hours. The solid product was obtained by filtration. The solid product was filtered and washed with chilled toluene (two times 25 ml). The solid product was kept under vacuum till the toluene was completely removed from the product. The wet weight of the solid product was 120 gram. The product is then dried at 60-70° C. and weighed again. The dry weight was 90-95 gram. The yield was 70%. The purity of the product as determined by HPLC was >98%. The melting point was 139-144° C.

Comparative Example 1 Preparation of 9,9-bis(hydroxymethyl)fluorene

Dimethylsulfoxide (DMSO) (400 ml) and paraformaldehyde (PF) (40 gram) were charged into a round bottom flask, mixed and cooled to a temperature of 13-15° C. Subsequently, sodium methoxide 30% solution (26 gram) was added to this mixture.

Gradually fluorene in powder form (100 gram) was added to above reaction mixture over a period of 15 minutes, while the temperature was maintained at 14-16° C. It was observed that most of the paraformaldehyde dissolves instantly upon addition of the fluorene. The resulting mixture was stirred for 30 minutes while the temperature was maintained at 14-16° C. The resulting mixture was a clear pale yellow solution.

Subsequently, concentrated HCl (8-10 ml) was added to the obtained solution until al neutral pH (pH 6-7) was reached in order to stop the reaction. The following work up was carried out for the reaction mixture: a large 3-5 liter round bottom flask was charged with water (1200 ml). The reaction mixture was slowed added to the water under stirring. The resulting mixture was stirred for 30 minutes at room temperature. The solid crude reaction product was obtained by filtration.

To the crude product toluene (350 ml) was added. The mixture was heated to 80-90° C. The heating was stopped and the mixture was allowed to return to room temperature. Then the mixture was further cooled to 10° C. and maintained at that temperature for 2 hours. The solid product was filtered and washed with chilled toluene (two times 25 ml). The solid product was kept under vacuum till the toluene was completely removed from the product. The wet weight of the solid product was 150 gram. The product is then dried at 60-70° C. and weighed again. The dry weight was 85-93 gram. The yield was 63%. The purity of the product as determined by HPLC was >98%. The melting point was 139-144° C.

Method of Preparing 9,9-bis(methoxymethyl)fluorene Based on the 9,9-bis(hydroxymethyl)fluorene Obtained in (comparative) Example 1

Sodium hydroxide (NaOH) (100 gram) was dissolved in water (100 ml) in a 2 liter round bottom flask under stirring. The reaction mixture was allowed to cool to room temperature. To this were added 9,9-bis(hydroxymethyl)fluorene (100 gram) obtained from either example 1 or comparative example 1, tetrabutylammonium bromide (2 gram) and toluene (500 ml). The resulting mixture was stirred at room temperature for 2-3 hours. At this stage the reaction mixture changed in nature and had become a thick paste.

The addition of the methylation agent, dimethyl sulfate (DMS) was carried out in four equal lots, each at a temperature of between 20-30° C. Each lot was added over a period of between 30-40 minutes in a drop wise manner. After each addition the resulting mass was stirred for 90 minutes before starting the addition of another lot. After all lots were added, the mass was stirred at the same temperature for another 20-24 hours. The solid paste dissolved and the color of the toluene layer became pale yellow.

Water (250 ml) was then added and the mixture was stirred for 15 minutes. The organic layer was separated and washed with water (200 ml). Toluene was distilled and traces thereof were removed by vacuum. To the solid residue methanol (200 ml) was added and this was refluxed for 15-30 minutes. The heating was stopped and the reaction mixture was cooled to 10° C. and maintained at that temperature for 2 hours. The product was filtered and washed with chilled methanol (two times 25 ml). The wet weight was 85 gram. The product was then dried 50-60° C. under vacuum to give a dry weight of 75-80 gram for comparative example 1 and 80-85 gram for example 1. The purity observed by HPLC was >99% for comparative example 1 and >99% for example 1. The yield was 80% for comparative example 1 and 85% for example 1.

The above results clearly show that with the process according to the present invention still produces good yields and purity while simplifying the process of step 1 significantly and reducing the amount of DMSO used. So a reduction in time and costs and environmental pollution may be obtained while still obtaining sufficient purity and yield. Hence one or more of the above aims are achieved by the present invention as disclosed in the appended claims.

It is noted that the invention relates to all possible combinations of features recited in the claims. Features described in the description may further be combined. 

1. A process for the synthesis of 9,9-bis(hydroxymethyl)fluorene from fluorene comprising providing a mixture of paraformaldehyde, dimethylsulfoxide, and toluene and a sodium alkoxide and adding fluorene as a solid to said mixture to obtain 9,9-bis(hydroxymethyl)fluorene.
 2. The process according to claim 1, wherein toluene is present in an amount of at most 600 milliliters per mole of fluorene used and/or in an amount of at least 400 milliliters per mole of fluorene used.
 3. The process according to claim 1, wherein fluorene is added in the form of a powder.
 4. The process according to claim 1, wherein dimethylsulfoxide is present in an amount of at most 600 milliliters per mole of fluorene used used and/or in an amount of at least 400 milliliters per mole of fluorene used.
 5. The process according to claim 1, wherein paraformaldehyde is used in an amount of between 1.8 and 2.6 mole per mole of fluorene used.
 6. The process according to claim 1, wherein said sodium alkoxide is selected from sodium methoxide and sodium ethoxide and/or—wherein said sodium alkoxide is used as a sodium alkoxide solution in an alcoholic solution.
 7. The process according to claim 1, comprising the following steps: a) providing a mixture of paraformaldehyde, dimethylsulfoxide and toluene; b) adding a sodium alkoxide solution in an alcoholic solvent to the mixture of step a); c) adding fluorene as a solid to the mixture obtained in step b); d) allowing the mixture obtained in step c) to react; e) quenching the mixture obtained in step d) by adding an acid; f) mixing the mixture obtained in step e) with water to obtain a suspension of 9,9-bis(hydroxymethyl)fluorene; g) filtering said mixture of step f) to obtain 9,9-bis(hydroxy-methyl)fluorene.
 8. The process according to claim 7, wherein the 9,9-bis(hydroxymethyl)fluorene obtained in step g) is not subjected to one or more purification step.
 9. The process according to claim 7, wherein the acid used to quench the mixture in step e) is an inorganic acid.
 10. The process according to claim 7, wherein water is added during step f) in an amount of between 1250 and 5000 milliliters water per mole of fluorene used.
 11. The process according to claim 1, wherein the process is carried out at a temperature between 10 and 20° C.
 12. The process according to claim 1, comprising the following steps: 1) providing a mixture of between 1.8 and 2.6 mole of paraformaldehyde per mole of fluorene used and at most 500 milliliters of dimethylsulfoxide per mole of fluorene used and at most 500 milliliters toluene per mole of fluorene used; 2) adding a sodium alkoxide solution in an alcoholic solvent to the mixture of step 1) so that the amount of sodium alkoxide is between 0.2 and 0.3 mole per mole of fluorene used; 3) over a period of between 5 and 30 minutes adding fluorene in the form of a powder to the mixture obtained in step 2) at a temperature between 10 and 20° C.; 4) allowing the mixture obtained in step 3) to react for a period of between 10 and 50 minutes at a temperature of between 10 and 20° C.; 5) quenching the mixture obtained in step 4) by adding an acid in an amount of between 10 and 20 milliliters per mole of fluorene used; 6) mixing the mixture obtained in step 5) with water in an amount of between 1250 and 5000 milliliters water per mole of fluorene used for a period of between 10 and 50 minutes to obtain a suspension of 9,9-bis(hydroxymethyl)fluorene; 7) filtering said mixture of step 6) to obtain 9,9-bis(hydroxy-methyl)fluorene.
 13. A process for the synthesis of 9,9-bis(methoxymethyl)fluorene from fluorene comprising: I) providing a mixture of paraformaldehyde, dimethylsulfoxide, toluene and a sodium alkoxide and adding solid fluorene to said mixture to obtain 9,9-bis(hydroxymethyl)fluorene; and II) providing an alkali metal hydroxide solution, mixing said solution with tetra-alkylammonium halide, 9,9-bis(hydroxymethyl)fluorene obtained in step I) and a solvent and adding dimethyl sulfate to obtain 9,9-bis(methoxymethyl)fluorene wherein dimethyl sulfate is added in at least three portions wherein the reaction mixture is stirred for a certain period before the following portion is added.
 14. The process according to claim 13, wherein step I) comprises: a) providing a mixture of paraformaldehyde, dimethylsulfoxide and toluene; b) adding a sodium alkoxide solution in an alcoholic solvent to the mixture of step a); c) adding fluorene as a solid to the mixture obtained in step b); d) allowing the mixture obtained in step c) to react; e) quenching the mixture obtained in step d) by adding an acid; f) mixing the mixture obtained in step e) with water to obtain a suspension of 9,9-bis(hydroxymethyl)fluorene; g) filtering said mixture of step f) to obtain 9,9-bis(hydroxy-methyl)fluorene; and wherein step II comprises the sub steps of h) providing a solution of sodium hydroxide in water; i) adding to the solution of step h) 9,9-bis(hydroxymethyl)fluorene, tetra-alkylammonium halide and a solvent; j) stirring the mixture obtained in step i); k) adding dimethyl sulfate in at least three portions, wherein the resulting reaction mixture obtained is stirred for a certain period of time before the following portion is added; l) continue stirring the reaction mixture obtained in k); m) adding water to the mixture obtained in step l) and stirring; n) separate the mixture obtained in step m) in an organic layer and a water layer, obtain the organic layer and wash the organic layer with water; o) separate the mixture obtained in step n) in an organic layer and a water layer, obtain the organic layer and remove the solvent to obtain crude 9,9-bis(methoxymethyl)fluorene.
 15. The process according to claim 13, wherein step 1 comprises: 1) providing a mixture of between 1.8 and 2.6 mole of paraformaldehyde per mole of fluorene used and at most 500 milliliters of dimethylsulfoxide per mole of fluorene used and at most 500 milliliters of toluene per mole of fluorene used; 2) adding a sodium alkoxide solution in an alcoholic solvent to the mixture of step 1) so that the amount of sodium alkoxide is between 0.2 and 0.3 mole per mole of fluorene used; 3) over a period of between 5 and 30 minutes adding fluorene in the form of a powder to the mixture obtained in step 2) at a temperature between 10 and 20° C.; 4) allowing the mixture obtained in step 3) to react for a period of between 10 and 50 minutes at a temperature of between 10 and 20° C.; 5) quenching the mixture obtained in step 4) by adding an acid in an amount of between 10 and 20 milliliters per mole of fluorene used; 6) mixing the mixture obtained in step 5) with water in an amount of between 1250 and 5000 milliliters water per mole of fluorene used for a period of between 10 and 50 minutes to obtain a suspension of 9,9-bis(hydroxymethyl)fluorene; 7) filtering said mixture of step 6) to obtain 9,9-bis(hydroxy-methyl)fluorene; and wherein step II comprises the sub steps of: 8) providing a solution of between 40 and 50 wt. % of sodium hydroxide in water so that between 2.5 and 7.5 mole of sodium hydroxide is present per mole of 9,9-bis(hydroxymethyl)fluorene—obtained in step 7) used; 9) adding to the solution in step 8) the following: 9,9-bis(hydroxymethyl)fluorene obtained in step 7), tetra-n-butylammonium bromide in an amount of 0.005 and 0.025 mole per mole of 9,9-bis(hydroxymethyl)fluorene used and adding toluene in an amount of between 800 and 1500 milliliter per mole of 9,9-bis(hydroxymethyl)fluorene used; 10) stirring the mixture obtained in step 9) for a period of between 1 and 5 hours at a temperature between 15 and 30° C.; 11) adding dimethyl sulfate in a total amount of between 2 and 6 moles per mole of 9,9-bis(hydroxymethyl)fluorene in between 3 to 6 portions, wherein each portion is added over a period of between 15 and 60 minutes and wherein the resulting reaction mixture is stirred for a period of between 60 and 120 minutes before the following portion is added and wherein the addition is carried out at a temperature between 15 and 35° C.; 12) continue stirring the reaction mixture obtained in 11) for a period of between 16 and 30 hours at a temperature between 15 and 35° C.; 13) adding water to the mixture obtained in step 12) in an amount of between 400 and 750 milliliter per mole of 9,9-bis(hydroxymethyl)fluorene used and stirring for a period of time between 5 and 25 minutes at a temperature between 15 and 35° C.; 14) separate the mixture obtained in step 13) in an organic layer and a water layer, obtain the organic layer and wash the organic layer with between 100 and 500 milliliter water per mole of 9,9-bis(hydroxymethyl)fluorene used; 15) separate the mixture obtained in step 14) in an organic layer and a water layer, obtain the organic layer and remove the solvent by distillation to obtain crude 9,9-bis(methoxymethyl)fluorene; and 16) optionally recrystallize the crude 9,9-bis(methoxymethyl)fluorene from between 300 and 600 milliliter methanol per mole of 9,9-bis(hydroxymethyl)fluorene used and dry under vacuum to obtain 9,9-bis(methoxymethyl)fluorene.
 16. The process according to claim 2, wherein toluene is present in an amount of at most 500 milliliters per mole of fluorene used.
 17. The process according to claim 4, wherein dimethylsulfoxide is present in an amount of at most 500 milliliters per mole of fluorene used.
 18. The process according to claim 6, wherein said sodium alkoxide is sodium methoxide.
 19. The process according to claim 9, wherein the inorganic acid is hydrochloric acid.
 20. The process according to claim 13, wherein in step I) 9,9-bis(hydroxymethyl)fluorine is obtained by the process according to
 1. 